test15_a.c

进程间调度

#include "test15.h"

char * fun_itoa(int i);

int main(int argc, char *argv[])
{
 int i, sta;
 long N;
 int pid, shm_id;
 struct PInfo *shm_addr;
 if(argc != 2)
   {
    printf("agrc error!!!\n");
    exit(0);
   }
 N = atol(argv[1]);
 if(N < 4)             /*要求输入的N值>=4*/
   {
    printf("the N  should >= 4\n");
    exit(0);
   }

 shm_id = shmget(SHM_KEY, sizeof(struct PInfo)*5, IPC_CREAT|0600);
 if(shm_id == -1)       /*创建共享内存，并获得共享内存的id*/
   {
    printf("shmget faild in main() !!!\n");
    exit(0);
   }
 shm_addr = shmat(shm_id, 0, 0);
 if(!shm_addr)         /*求和进程与共享内存相连，并得到首地址*/
   { 
    printf("shmat faild in main() !!!\n");
    exit(0);
   }
 
 shm_addr[0].pstatus = 'X';     /*对共享内存中各进程的状态位初始化*/
 shm_addr[1].pstatus = 'X';
 shm_addr[2].pstatus = 'X';
 shm_addr[3].pstatus = 'X';
 shm_addr[4].pstatus = 'X';

 if((pid=fork()) == -1)
   {
    printf("fork faild !!!\n");
    exit(0);
   }
 if(!pid)      /*创建子进程，用于从消息队列获取消息，重新创建求和进程或并行计算进程*/
     execl("/root/test15_b", "test15_b", argv[1], (char *)0);
   
 if((pid=fork()) == -1)
   {
    printf("fork faild in main() !!!\n");
    exit(0);
   }
 if(!pid)      /*创建求和进程*/
    execl("/root/test15_c", "test15_c", argv[1], (char *)0);

 for(i=1; i<=4; i++)         /*创建四个并行计算进程*/
    {
     pid = fork();
     switch(pid)
           {
            case -1:
                    printf("fork faild in main() !!!\n");
                    exit(0);
            case  0:
                    execl("/root/test15_d", "test15_d", fun_itoa(i), (char *)0);
                    break;
            default:
                    ;
           }
       
    }
 if(shmdt(shm_addr) == -1)     /*父进程与共享内存脱离*/
    printf("shmdt faild in main() !!!\n");
}
/*
char * fun_itoa(int i)

返回值：char型指针，即字符串
参数：i    int型变量
函数功能：得到int变量的字符串形式。
*/
char * fun_itoa(int i)
{
 switch(i)
       {
        case 1: return "1";
        case 2: return "2";
        case 3: return "3";
        case 4: return "4";
       }
}